The present invention relates, in general, to devices and methods for inducing controlled cracks in concrete to avoid unsightly cracks on the outer surface of concrete structures.
U.S. Pat. No. 5,918,428, which is incorporated here by reference, was issued to the inventor of the present invention on Jul. 6, 1999. This patent discloses a crack inducer plate assembly for concrete structures that includes an elongated, rigid core plate for extending in concrete at a location spaced from the surface of the structure, and a waterproof, resilient water-stop member fixed to and covering at least part of the core plate. Cross plates are welded to the core plate to anchor the core plate to reinforcing bars in the concrete, and the inventor discovered that cracks were formed in a controlled manner within the concrete volume.
When concrete shrinks during the hydration period, stress in the concrete is relieved by cracking. The cracking is addressed in many ways depending on the conditions or use, for example by providing elongated reveals such as V-shaped or polygonal members of grooved at the surface of the concrete. In most structural concrete, cracking is expected and is not a problem unless the surface is subject to water intrusion, is exposed to view, or both. Then, the issue of cracking becomes important.
A search was conducted at the USPTO in preparation for this disclosure. The search encompassed United States patents categorized under the following U.S. patent classifications: Class 52, Subclasses 127.3, 393, 396.02, 396.05, 601 and 742.14; and Class 404, Sunclasses 47 and 55.
In addition to U.S. Pat. No. 5,918,428 mentioned above, the most pertinent patents found in the search were the following:
U.S. Pat. No.Inventor(s)2,167,904Older2,961,803Shapiro et al.3,411,260Dill3,501,877White3,575,094Hewitt et al.3,596,421Miller3,871,787Stegmeier4,050,206Utsuyama4,090,800Koch4,128,358Compton4,329,080Elley4,362,427Mass et al.4,388,016Levey4,979,846Hill et al.5,375,386Goad5,956,912Carter et al.
U.S. Pat. No. 2,961,803 to Shapiro et al. discloses a combined joint-former and water barrier which is formed of steel, and preferably galvanized steel for corrosion resistance. The joint-former portion includes a strip erected vertically, which has an outer flange bent at a right angle and perforated for nailing to an outer form of the vertical concrete foundation wall. An edge of the joint-former is accommodated within sharply creased V-shaped fold at the mid-portion of a vertical water barrier strip. The V-shaped fold has an apex. The vertical water barrier strip has edge portions with anchoring bent flanges at its extremities adapted for bonding to the concrete and stoppage of water passage. This patent does not disclose a flange connected to a core plate for reducing a tendency for a crack in the volume from propagating from the flange portion nor a water-stop with large beads at the ends of overhanging projections.
U.S. Pat. No. 4,362,427 to Mass et al. discloses a resilient sealing strip for expansion joints in concrete. The strip has three pairs of fins including one pair of fins that form a “T” shape at one end.
U.S. Pat. No. 3,871,787 to Stegmeier discloses a joint structure including a plastic T-shaped channel and a vertical web extending downward from the channel. The vertical web is equipped with anchors disposed at right angles with respect to the vertical plane of the web. The anchors have a horizontal web ending in a vertically oriented flange. The vertical web tapers downwardly to a relatively sharp point or edge that facilitates penetration of the concrete mass by the joint structure.
Other T-shaped control joints are described in U.S. Pat. No. 4,128,358 to Compton and U.S. Pat. No. 4,090,800 to Koch.
Other joint devices were also uncovered. For example, U.S. Pat. No. 2,167,904 to Older discloses a concrete expansion and contraction joint constructed of sheet metal including a parting plate, which is provided to assure the formation of a crack and a dowel plate that projects horizontally from the parting plate into the concrete. Both plates are supported by clamping members which serve as anchoring members. A flange is connected at a right angle to the clamping members. Older '904 does not disclose a resilient water-stop member attached to the clamping member with flange or large beads on a projecting member of a water-stop.
U.S. Pat. No. 5,956,912 to Carter et al. discloses a plastic control joint for controlling concrete structures and cracking. The control joint includes an upstanding web member that extends vertically from a base divided into oppositely extending flanges. Each flange is disposed at a right angle with respect to the upstanding web member. The upstanding web member tapers into an upper edge corner. Arms extend from the web at an intermediate elevation. The flanges have apertures at spaced apart locations to accept ground stakes.
U.S. Pat. No. 3,575,094 to Hewitt discloses a hollow plastic expansion joint and water lock having a U-shaped portion connected to the sidewalls of a V-shaped end with an apex. Lateral flanges having grooved beads project from the sidewalls for anchoring the flanges in concrete.
U.S. Pat. No. 4,979,846 to Hill et al. discloses a contraction joint comprising a base, a central projection extending upwardly from the base with an upper apex section, and a plurality of water stops attached to the base. The water-stops extend upwardly from the base and are characterized by round-shaped tops.
U.S. Pat. No. 3,501,877 to White discloses a joint spacer having a V-shaped body having diverging legs with holes for allowing mortar to flow through the holes to form a bond through and around the spacer.
The remaining patents are cited for general reference.
Although the concept of controlling cracking in concrete floors, that is, generally horizontally extending concrete strictures, has been accepted, the control of cracking in generally vertically concrete structures such as walls, piers, columns and beams, has not.
An article by the present inventor, “Cracking in Architectural Concrete,” Reginald D. Hough, Concrete Industry Board Bulletin, 1999, discusses some of his original thinking on the subject.
The present disclosure seeks to improve on that thinking and to provide a new invention that reflects his further understanding and discovery in this field.